Exhaust gas discharged from an internal combustion engine of, for example, an automobile contains toxic components such as HC, CO, and NOx (nitrogen oxides). Hitherto, three-way catalysts have been used for removing such toxic components for detoxifying the exhaust gas. Among such three-way catalysts, some catalysts are formed of a catalyst member material having an OSC for mitigating variation in oxygen concentration of exhaust gas, to thereby efficiently remove HC, CO, and NOx. An example of the material having OSC is a CeO2—ZrO2 solid solution compound (see, for example, Patent Documents 1, 2, and 3). Meanwhile, oxygen storage capacity is known to be provided by a change of Ce valence. Studies have been carried out on CeO2—ZrO2 catalyst member material so as to enhance heat resistance and prevent sintering of noble metal supported on the carrier, by employing different compositional proportions between the particle core and the particle surface (see, for example, Patent Document 4).